Flame proof thermostat box

ABSTRACT

A flame proof box to contain any one of several commercially available thermostat switches with a readily removable strap support for the switch; readily removable flame-proof means to conduct the wires and the capillary tube of the thermostat through the walls of the box; and a flame-proof means through the removable cover of the box for adjustment of the thermostat, that has a lost motion, positive-connection, clutch device that enables the cover to be secured in place and the clutch elements to be interengaged without pre-alignment of the clutch elements.

United States Patent [191 Kaesser et al.

[ June 12, 1973 FLAME PROOF THERMOSTAT BOX [75] Inventors: Glenda F.Kaesser, St. Louis;

Marshall G. Zavertnik, Manchester, both of Mo.

[73] Assignee: Killark Electric Manufacturing Company, St. Louis, Mo.

[22] Filed: Sept. 30, 1971 [21] Appl. No.: 185,319

[52] US. Cl. 200/168 G, 337/380 [51] Int. Cl. ,H01h 21/08 [58] Field ofSearch 200/168 G; 337/112,

[56] References Cited UNITED STATES PATENTS 3,265,848 8/1966 Reik200/168 G 3,385,945 5/1968 Tums 200/168 G 2,345,757 4/1944 LesterZOO/168 G 5/1941 Bissell 200/168 G 8/1966 Farina et al 200/168 G XPrimary Examiner-Robert K. Schaefer Assistant Examiner-William J. SmithAttorneyRogers, Ezell, Eilers & Robbins [5 7] ABSTRACT A flame proof boxto contain any one of several commercially available thermostat switcheswith a readily removable strap support for the switch; readily removableflame-proof means to conduct the wires and the capillary tube of thethermostat through the walls of the box; and a flame-proof means throughthe removable cover of the box for adjustment of the thermostat, thathas a lost motion, positive-connection, clutch device that enables thecover to be secured in place and the clutch elements to be interengagedwithout prealignment of the clutch elements.

13 Claims, 7 Drawing Figures FLAME PROOF THERMOSTAT BOX BACKGROUND OFTHE INVENTION A primary purpose of the invention is to overcome priorart requirements of a different box for each thermostat switch, byproviding a single box that, with simple selection of a few auxiliaryparts, can be used with any of several commercially availablethermostats. The basic box is uniform, and it can receive any of severalswitch-supporting straps shaped to be attached to the box by uniformattaching means, usually screws, in a manner to hold the particularswitch in place in the box with its adjustment shaft in a predeterminedposition relative to the box that is the same for all switches.

Additionally there are uniform, flame-proof fittings to conduct theswitch wires as well as the capillary tube through the walls of the box,that can be easily adapted by choice of auxiliary fittings, toaccommodate various sizes and arrangements of wires and capillaries.

There is also a position clutch arrangement that has interlocking partsbetween the box cover and the thermostat adjusting shaft that can beadapted to the particular thermostat by a simple threaded adjustment,and the substitution of a simple auxiliary part proper for the selectedthermostat.

This clutch arrangement has a further advantage that, though flame-proofand though requiring position interlocking of parts on the cover andparts fixed in the box, the interlocking parts are constructed to enablethe cover to be fastened onto the box without prealignment of the clutchelements, which can thereafter be interlocked and maintained ininterlocking position by a simple operation of the adjusting memberoutside the box.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the device;

FIG. 2 is an enlarged vertical section on the line 22 of FIG. 1;

FIG. 3 is a top view of the box with the cover removed;

FIG. 4 is an enlarged diametrical section through the thermostatadjustment connection;

FIG. 5 is a bottom view of a portion of the thermostat adjustmentconnection taken on the line 5-5 of FIG.

FIG. 6 is a diametrical section of a portion of the thermostatadjustment connection taken at right angles to the showing of FIG. 4 andon the line 6-6 thereof; and

FIG. 7 is a plan view of a connecting element for the thermostatadjustment.

DESCRIPTION OF THE PREFERRED EMBODIMENT This box 10 is designed to meetthe requirements of explosion-proof receptacles. It has a bottom wall11, end walls 12 and 13, side walls 14 and 15 with inwardly projectingflanges 16 around the top edges of these side and end walls. There is acover 18 that can be attached or removed from the box. The cover is heldin place by four screws 19 that can be threaded into screw holes 20 inthe corners of the box. The flange 16 at the top is oppositely recessedat 24 and 25 to provide ledges for a purpose to be described.

Adjacent the bottom the box may have ears 27 and 28 through which holesmay be provided to receive bolts or screws for attachment of the box toa support. In the preferred form, the box is cast metal, for example,aluminum. The interfaces between the cover and the box are ground smoothso that when the enclosure is assembled a 0.0015 inch feeler gauge willnot enter the joint between the box and cover more than oneeighth of aninch.

Within the box a U-shaped thermostat mounting strap 30 has outwardlyturned ends engaging the ledges within the recesses 24 and 25 andsecured thereto by screws 31. This strap is of a size appropriate tomount a thermostat 33, here illustrated as being secured below the strapby screws 34. The box is of a size that can accommodate any of a numberof regular commercial thermostats when a strap 30 appropriate thereto isprovided. Each of these thermostats has an adjusting shaft 37, and thestraps are sized and shaped so that shafts of all of the differentthermostats will project toward a particular spot inside the cover 18.The rotation of the shaft 37 backward or forward adjusts the thermostatin the known manner.

The shaft 37 may be provided with a flat side for connection with arotating knob or the like. In the event that the thermostat contains asocket instead of a shaft 37, the shaft 37 is a stub shaft provided withmeans to engage into the thermostat and to return the adjusting membersthereof.

The present invention provides flame-proof connecting means leadingthrough the cover of the box to provide for adjustment of the thermostatfrom outside the box. To this end the cover of the box has a tappedopening medially through it which receives a fitting 40 threaded intothe proper position and locked into place by a nut 41. The threads arelong enough and tight enough to meet flame-proofing standards.

Through the axis of this fitting 40 there is a smooth bored hole thatreceives with a close fit a smooth shaft somewhat longer than thethickness of the fitting. These parts are made long enough and withclose enough fits to meet flame-proof standards. The shaft 42 is groovedat its ends to receive snap-in rings 43 and 44. These snap rings 43 and44 are spaced apart a distance to permit a limited axial movement of theshaft 42 through the fitting 40. A kerf 45 or other equivalent meanssuch as a knob is provided in the outer end of the shaft 42 to permitthe shaft to be adjusted by rotat- The inner end of the shaft receives aconical coil spring 48 that is held in place under compression by aremovable collar 49. This collar may have set screws, as illustrated, tohold it in place but to permit it to be removed. The collar 49 has across pin 50 integrally attached to its under side, as by welding. Thecoil spring 48 urges the shaft inwardly of the box but permits aresilient displacement of the shaft outwardly, all of this movementbeing within the limits provided by the two spring rings 43 and 44.

The thermostat adjusting shaft 37 likewise has a collar 54 secured toits outer end as by set screws. The collar 44 has a cross pin 55integrally attached to its upper end as by welding.

An interconnecting, oppositely slotted clutch elementor connector 56,here shown as being made of an electrically insulating plastic material,is interposed between the collars 49 and 54. This connector 56 hastransverse slots 57 and 58 in its upper and lower surfaces,respectively, that are of a size to receive the two cross pins 50 and 55of the collars 49 and 54.

When the connector 56 is in place between the two collars 49 and 54, thecross pins 50 and 55 normally are in their respective slots of theconnector 56, so that rotation of the externally projecting shaft 42 istransmitted by a positively driven interconnection through the connector56 to cause rotation of the thermostat adjusting shaft 37.

Thermostats of the present kind are controlled by bulbs 60 located atthe point at which the temperature is to be regulated. The bulb 60 isconnected by a capillary tube 61 into the thermostat in a manner knownin the art.

In the present box, a fitting is provided to insure that the capillaryis introduced into the box without permitting transmission of flamethrough the wall of the box, and yet in a manner to permit thethermostat to be removed at will through the top opening of the boxwithout cutting the capillary tube. To this end the wall 13 is drilledand tapped to receive a nipple 70 that is threaded through the wall insuch a fashion as to prevent transmission of flame. The interior of thefitting 70 is of a smooth, tapered contour and it receives two identicalsemi-conical members 71 of the same taper, that can be fitted togetherto form a full frustum of a cone.

Each of the semi-conical members 71 is provided with a semi-cylindricalaxial groove 72 extending from end to end of the members, and aprojecting semicylindrical boss or projection 73. When the twosemiconical members 71 are placed together, forming the full frustum ofa cone, the two semi-cylindrical grooves 72 provide a cylindrical holethat fits closely about the capillary tube 71, and the two bosses 73form a cylindrical projection on the outer end of the cone. A cap nut 74is threaded over the two members 71 and onto the fitting 70. As shown,it has a hole which receives two bosses 73 thereby aiding in centeringthe cone, and when the cup is threaded onto the nipple 70, it pressesthe two members of the cone into the complementary conical surface ofthe fitting 70. This inward pressure forces the two members together sothat their interfaces are in a snug relationship and so that they engageabout the capillary tube 61 with a snug fitting. The surfaces arefinished and sized so as to prevent the transmission of flame betweenthe inside and the outside of the box in any way through the fitting.The cap nut 74 can be secured in position by a lock screw as isindicated.

Commercial thermostats of this type have two different kinds of lead.Some have terminals within the box to which leads are brought throughthe wall of the box and connected. These leads may be carried throughthe box will in a fitting in which they are plotted in a conventionalfashion, since they can stay permanently in the box. However, there arecommercial thermostats which are provided with longer leads permanentlyconnected internally to the thermostat, and which must be carriedthrough the wall of the box and connected outside the box. To removethis type of thermostat from the box, these leads must be withdrawnthrough the wall of the box. The present box accommodates these withoutrequiring destruction of the potting.

The box is drilled and tapped through the end 12, and a tubularexternally threaded fitting 80 is secured in the opening in such amanner as to prevent transmission of flame through the threaded portion.The fitting 80 is provided with external threads on its outer end sothat it can be connected in flame-proof manner with a regular conduit.

The fitting 80 has a smooth cylindrical inner surface to receive anequally smooth cylindrical or tubular member 82. This member can be heldin place by snap rings 83 and 84 on its opposite ends, preferablyallowing some free endwise play. Wires 85 pass through the tubularfitting 82 and are potted in place as by potting compound 86 against anelectric washer 87. A strip of tape 88 may confine the wires to thebracket and the thermostat 33.

USE

In use, the thermostat 33 is mounted on the strap 30 by the screws 34.By simply selecting the proper U- strap 30 suitable to the made ofthermostat at hand, the user may mount any of several commercialthermostats in this one sized box. All of the straps dispose screw holesto receive the screws 31. All dispose the adjusting shafts 37 to beaxially aligned with the shaft 42 in the cover 18.

If the lead-in wires 85 are as shown, they are passed through the tubeor sleeve 82 and are potted therein by the positioning compound 86,which completely seals the tube against transmission of flame throughit. This potting compound can be applied either before or after thethermostat is assembled in the box. Obviously only one sized sleeve maybe provided, as it is large enough for all thermostat wire combinations.But to reduce the cross section of potting compound, a sleeve withsmaller internal diameter and the same external diameter may be usedwithout requiring a change in the fitting 80. The sleeve 82, with thesnap ring 83 removed, is inserted into the fitting 80, and the snap ring83 put into its groove on the outer end of the sleeve, so that thesleeve is confined against withdrawal. The fit between the outer wall ofthe sleeve and the fitting 80 is such that it will inhibit thetransmission of flame through the wall 12.

The thermostat bulb must be passed through the wall 13 when thethermostat 33 is installed in the box. The small end of the conicalfitting is large enough to pass any of the standard bulbs. After thebulb is thus passed through the fitting 70, the capillary 61 is drawn asstraight as can be done easily, and the two semiconical members 71,selected to provide the proper axial hole diameter for the particularthermostat capillary, are placed around the capillary 61 with thenotches 72 embracing it. The members 71 are then pushed by hand into thefitting 70 and the cap nut 74 screwed into place. The cap nut drives thetwo members 71 together so that their interfaces are in closeassociation and so that the two grooves 72 closely embrace the capillary61, all with fits of adequate length and closeness to preventtransmission of flame through the wall 10. The final straightening outof the capillary within the hole through the members 71 is produced bythe squeezing action of the members.

The cap nut 74 is turned down tightly enough to insure the foregoing,and may be held against becoming loose by a set screw as indicated.

With the wires 85 in place in the fitting and the capillary 61 in thefitting 70, 'as described, the ends of the strap 30 are screwed down bythe screws 31 to secure the thermostat in the box. When it is desired toremove the thermostat for servicing or replacement, it is necessary toremove the screws 31, loosening the strap that supports the thermostat,to remove the cap nut 74 and the two conical wedges 71 from about thecapillary 61, and to spring the retaining ring 83 from the tube 82,freeing it and the wires 85 (provided their external junctions have beendisconnected). Then the strap, with thermostat, wires, and bulb can beremoved from the box.

A particular feature of this application resides in the manner in whichthe adjusting means is made that permits the quick application of thecover 18 to the box 10. An appropriate collar 54 is secured onto thethermostat shaft 37, and the connector 56 is placed onto the collar 54with the notch 58 over the cross pin 55. The cover 18 is prepared byattaching a collar 49 of appropriate inside diameter to the shaft 42,and loosening the nut 41 and screwing the fitting in or out of to anestimated position suitable to permit the interlock of the bar into theslot 57 of the connector 56 when the shaft 42 is displaced outwardlyagainst the spring 48, and the cover 18 is in attached position. Thelock nut 41 is tightened to maintain this relationship. The cover 18with the screws 19 loose, is placed into its proper position on the box.

When the cover is put into place, the upper cross pin 50 may not berotated into position to fit into the slot 57. The cover maynevertheless be pressed down into position and the screws 19 at leastpartially engaged with the appropriate holes in the box. With the pin 50out of registry with the slot 57, the shaft 42 is displaced outwardly,further compressing the spring 48, this being permitted by the spacingof the snap ring 44. Preferably, this snap ring permits enough outwardmovement of the shaft 42 to permit the cover to be placed down againstthe box even though the pin 50 is out of registry with the slot 57.

With this situation, the shaft 42 is rotated. As soon as the pin 50registers with the slot 57, it will be snapped into place therein underthe action of the spring 48 and will be held in such disposition by thefact that the spring remains partly under compression. Thereupon, thescrews 19 may be turned firmly into engagement and the mechanism will beretained in this position. Thus, it is not necessary to provide acareful prealignment and retaining of parts in pre-aligned position inthe assembly of the thermostat in the box.

The description has referred to a thermostat, as this uses most of thefeatures of this invention. Other devices having like rotary adjustingmeans may be installed in such a box. If they have wiring or tubularprojections or other equipment like those things, they may takeadvantage of the other features of the assembly, to wit, the pottingcompound fitting and the capillary tube fitting. Accordingly, in abroader sense, the enclosed device is referred to as one responsive tochanges in physical conditions, and in a specific and optimum sense, asa thermostat. In all cases, the assembly provides an enclosure for anexternally adjustable device having portions that must extend outsidethe enclosure, wherein the adjustment, as well as the passages to theoutside, are all flame-proof.

Various changes and modifications may be made within this invention aswill be readily apparent to those skilled in the art. Such changes andmodifications are within the scope and teaching of this invention asdefined by the claims appended hereto.

What is claimed is:

1. In a box to receive and mount any one of a plurality of mounteddevices responsive to physical conditions, each having an adjustingmember turnable back and forth; means to secure a mounted deviceremovably in the box with its adjusting member in a predeterminedposition with respect to a wall of the box, adjusting means mounted inthe wall of the box including a positive-engagement clutch, an axiallycompressible means, and a rotatable shaft passing through the said wall,the means to secure the mounted device in the box disposing theadjusting member thereof in interconnectable position relative to theadjusting means, the fit of the rotatable shaft and the length of itsinterengagement with the wall being such that flame passage through thewall is retarded, the positive-engagement clutch comprising axiallyseparable interengageable elements axially movable together intoengagement, the axially compressible means urging them into engagement,but permitting disposition of the mounted device in fixed position withrespect to the wall with them in an abutting disengaged position,rotation of the shaft from outside the wall then aligning the partswhereupon the yieldable means causes them to become interengaged so thatthey are clutched together and so that rotation of the shaft thereafterrotates the adjusting member.

2. In the box of claim 1: the axially compressible means comprising therotatable shaft and a mounting therefor through the wall permittinglimited axial displacement of the shaft, and spring means urging theshaft inward of the box to effect engagement of the clutch, the mountingproviding interfitting surfaces of closeness and length to retardtransmission of flame between inside and outside of the box.

3. In the box of claim 1: a mounting for the shaft in the wall having amember holding the shaft for its axial and rotary movement, the memberbeing secured to the wall for adjustment into and out of the wall, meanslimiting axial movement of the shaft in the member, the axial adjustmentproviding predetermined initial positioning of the shaft, and theconnection of the member in the wall having closeness and length toretard flame transmission.

4. In the box of claim 3: the member being threaded into the wall, andlock means to hold it in adjusted position in the wall.

5. In the box of claim 1: the wall being separable from the box, anddisconnectable attaching means for removably securing the wall onto thebox, the axially compressible means permitting the wall to be positionedand connected to the box without prior interengagement of the clutchingelements.

6. In the box of claim 1: the means to secure the mounted device in thebox comprising a removable element having prepositioned attaching meanswith the box so that other removable elements with like attaching meansbut different attachments to hold the mounted device may be attached, todispose different mounted devices with their adjusting members inpredetermined position for interengagement with the same adjusting meanson the box wall.

7. In the box of claim 1: the clutch including two collars, one on therotatable shaft, the second on the adjusting member of the mounteddevice, both being removable, and means for effecting drivinginterengagement between them, the means having positive driveinterfitting components.

8. In the box of claim 7: the last named means including a connectorbetween the two collars, and projection and socket means between eachcollar and the connector.

9. In the box of claim 1: the mounted device being a thermostat.

10. In the box of claim 9: the thermostat having a casing and anenlarged sensing element spaced from the casing and connected into it bya thin elongated memher; the box having an opening through a wall largeenough to permit the sensing element to pass through, and having meansfitting into the opening and engaging the thin elongated member, thesaid means having engagement with the box and with the thin member oflength and closeness to retard flame passage.

11. In the box of claim 10: the thermostat having wiring, and the boxhaving a hole through a wall through which the wiring can pass; andmeans engaged in the hole and about the wiring and removably engaged inthe hole through the wall, the said means having en-' gagement with thewiring and through the wall of length and closeness to retard passage offlame.

12. In a box to receive and mount a thermostat having a casing, anadjusting member, a sensing bulb connected into the casing by acapillary tube, and wiring connected into the casing; the box having anadjusting means through a wall connectable with the adjusting member ofthe thermostat, including a movable adjusting member having a fit closeand long enough to retard flame passage; the box having a wall openinglarge enough to pass the bulb, and removable means engageable thereinand removably engageable with the capillary tube with a fit close andlong enough to retard flame; one wall of the box being removable towithdraw the thermostat when the removable means engaging the capillaryis removed from the box and from the capillary tube.

13. In the box of claim 12: the thermostat having wiring, and the boxhaving a wiring opening through a wall, a tubular element about thewiring with sealing material molded in the tubular element about thewiring; means engaging the tubular element in the wall with a closenessand length to retard flame, the said means being removable with thewires and sealing material.

1. In a box to receive and mount any one of a plurality of mounted devices responsive to physical conditions, each having an adjusting member turnable back and forth; means to secure a mounted device removably in the box with its adjusting member in a predetermined position with respect to a wall of the box, adjusting means mounted in the wall of the box including a positive-engagement clutch, an axially compressible means, and a rotatable shaft passing through the said wall, the means to secure the mounted device in the box disposing the adjusting member thereof in interconnectable position relative to the adjusting means, the fit of the rotatable shaft and the length of its interengagement with the wall being such that flame passage through the wall is retarded, the positive-engagement clutch comprising axially separable interengageable elements axially movable together into engagement, the axially compressible means urging them into engagement, but permitting disposition of the mounted device in fixed position with respect to the wall with them in an abutting disengaged position, rotation of the shaft from outside the wall then aligning the parts whereupon the yieldable means causes them to become interengaged so that they are clutched together and so that rotation of the shaft thereafter rotates the adjusting member.
 2. In the box of claim 1: the axially compressible means comprising the rotatable shaft and a mounting therefor through the wall permitting limited axial displacement of the shaft, and spring means urging the shaft inward of the box to effect engagement of the clutch, the mounting providing interfitting surfaces of closeness and length to retard transmission of flame between inside and outside of the box.
 3. In the box of claim 1: a mounting for the shaft in the wall having a member holding the shaft for its axial and rotary movement, the member being secured to the wall for adjustment into and out of the wall, means limiting axial movement of the shaft in the member, the axial adjustment providing predetermined initial positiOning of the shaft, and the connection of the member in the wall having closeness and length to retard flame transmission.
 4. In the box of claim 3: the member being threaded into the wall, and lock means to hold it in adjusted position in the wall.
 5. In the box of claim 1: the wall being separable from the box, and disconnectable attaching means for removably securing the wall onto the box, the axially compressible means permitting the wall to be positioned and connected to the box without prior interengagement of the clutching elements.
 6. In the box of claim 1: the means to secure the mounted device in the box comprising a removable element having prepositioned attaching means with the box so that other removable elements with like attaching means but different attachments to hold the mounted device may be attached, to dispose different mounted devices with their adjusting members in predetermined position for interengagement with the same adjusting means on the box wall.
 7. In the box of claim 1: the clutch including two collars, one on the rotatable shaft, the second on the adjusting member of the mounted device, both being removable, and means for effecting driving interengagement between them, the means having positive drive interfitting components.
 8. In the box of claim 7: the last named means including a connector between the two collars, and projection and socket means between each collar and the connector.
 9. In the box of claim 1: the mounted device being a thermostat.
 10. In the box of claim 9: the thermostat having a casing and an enlarged sensing element spaced from the casing and connected into it by a thin elongated member; the box having an opening through a wall large enough to permit the sensing element to pass through, and having means fitting into the opening and engaging the thin elongated member, the said means having engagement with the box and with the thin member of length and closeness to retard flame passage.
 11. In the box of claim 10: the thermostat having wiring, and the box having a hole through a wall through which the wiring can pass; and means engaged in the hole and about the wiring and removably engaged in the hole through the wall, the said means having engagement with the wiring and through the wall of length and closeness to retard passage of flame.
 12. In a box to receive and mount a thermostat having a casing, an adjusting member, a sensing bulb connected into the casing by a capillary tube, and wiring connected into the casing; the box having an adjusting means through a wall connectable with the adjusting member of the thermostat, including a movable adjusting member having a fit close and long enough to retard flame passage; the box having a wall opening large enough to pass the bulb, and removable means engageable therein and removably engageable with the capillary tube with a fit close and long enough to retard flame; one wall of the box being removable to withdraw the thermostat when the removable means engaging the capillary is removed from the box and from the capillary tube.
 13. In the box of claim 12: the thermostat having wiring, and the box having a wiring opening through a wall, a tubular element about the wiring with sealing material molded in the tubular element about the wiring; means engaging the tubular element in the wall with a closeness and length to retard flame, the said means being removable with the wires and sealing material. 